1. Field of the Invention
The present invention is related to a cold forging forming method for forming a three-dimensional hollow article without rough edges, and especially to a cold forging forming method using an alloy of low melting point instead of mercury as a filler with plasticity, for saving expensive chilling equipment and providing another effect of easy management of operation; thereby cost of purchasing as well as forming can be effectively reduced, besides, latent public damage of pollution in the processing of forming can be eliminated, and safety of forming can thus be increased.
2. Description of the Prior Art
The inventor of the present invention has obtained a U.S. Pat. No. 5,884,516 "THREE DIMENSIONAL COLD FORGING METHOD FOR SHAPING A HOLLOW ARTICLE AND THE APPARATUS FOR THE METHOD". Wherein, liquid mercury is used as a freezing medium filled in the space between a die protecting member and the external wall of a seamless die cavity. The liquid mercury can be poured, discharged and recollected at normal temperatures but can have good stiffness after being frozen, thereby, the freezing medium can support the die cavity against forging pressure after being frozen. By the law of conservation of energy, and by the high plasticity of polyurethane, a polyurethane strip placed in a blank to be forged swages the blank when it is pressed to deform and expand by a forging press. In this way, the inner and external walls of the blank is shaped into the shape of a three dimensional seamless die cavity, thus troubles in producing three dimensional artistic articles can be solved.
However, cost of equipment for fast freezing in the markets is much higher than that of heating equipment. And freezing temperature of liquid mercury is -38.5.degree. C., thereby, liquid mercury is preferably to be fast frozen to -40.degree. C. in favor of shaping the cold forged blank, this induces increasing of cost in purchasing equipment. And energy consumption for freezing liquid mercury is much larger than that for the equipment for heating, thereby cost of production can be higher and tends to be a burden. And more, liquid mercury has high specific gravity and is a kind of expensive metal; it is fluid at normal temperatures. When in delivery, it is extremely subjected to generating spattering; this makes inconvenience in management by operators, and tends to create damage to human bodies and public pollution environmentally. Therefore, this forms a very large trouble in the process of forging three-dimensional hollow articles.